Hitachi 46W500, Training

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DP-3X HORIZONTAL DRIVE CIRCUIT EXPLANATION
PAGE 05-01
HORIZONTAL DRIVE CIRCUIT DIAGRAM DESCRIPTION:
(Use the Horizontal Drive Circuit Diagram for details)
CIRCUIT DESCRIPTION
When B+ arrives at the Rainforest IC I501 pin ( 45 ), horizontal drive is output from pin ( 37 ). The drive signal is
routed through the connector PPS3, PPD3 pin 6 to the Horizontal Driver Transistor Q709 . This transistor
switches the ground return for pin (
8
) of the Driver transformer (
T702
).
SW+28
volts is routed through
R748
and
R730 . Then through D715 and supplied to pin ( 5 ) as primary voltage. The switching of Q709 allows EMF to
develop. As this signal collapses, it creates a pulse on the output pin of ( T702 ) at pin ( 4 ) to the base of the De-
flection Horizontal output transistor Q777 . This transistor provides primary switching pulses for the Deflection
Transformer
T701
.
Q777 TRANSISTOR PRODUCES THE FOLLOWING OUTPUT PULSES;
1. The Dynamic Focus OUT Circuit to QF01 : A Dynamic Focus waveform, (Horz. Parabola) is created.
This is a parabolic waveform that is superimposed upon the static focus voltage to compensate for beam
shape abnormalities which occur on the outside edges of the screen because the beam has to travel fur-
ther to those locations.
2. Horizontal Deflection Yokes drive signals. The collector of Q777 provides the drive signal for all
Horizontal Deflection Yokes.
T701 TRANSFORMER PRODUCES THE FOLLOWING OUTPUT PULSES;
•
Deflection H. Pulse from pin (7): This pulse is used by;
HORIZONTAL BLANKING (H. BLK) GENERATED FROM PIN (7):
The Horizontal Pulse is also routed to the Horizontal Blanking generation transistor Q706 . This transistor gener-
ates the 13V P/P called H Blk . This signal goes to the following circuits;
• To the
PPD3, PPS3
connector pin
8
to pin (
39
) of
I501
as
FBP In.
Here this signal is used as a comparison
signal. It is compared to the reference signal coming in at pin ( 50 ) Horizontal Sync. If there are any differ-
ences between these two signals, the output Drive signal from pin ( 37 ) is corrected.
NOTE
: When a 1080i signal is input through component inputs, the Reference signal for Horizontal
Sync now becomes the H Sync before the Flex Converter. Output from sync selector I502 , pin ( 14) .
(See the Main/Component Sync Circuit Diagram for details).
•
The H Blk signal is also routed to the Microprocessor which uses this signal for OSD positioning and for
Station Detection during Auto programming within the coincidence detector, also as a detection signal to
activate the AFC Loop.
•
The PinP unit uses this signal for switching purposes. Like the read/write clock, positioning, etc…
• Through the
PDG
connector pin
14
to the Convergence circuit for correction waveform generation.
•
Through CN01 to the Sweep Loss Circuit ( QN01 ) to shut off the drive to the CRTs if Horizontal deflection
is lost.
H Blk for HORIZONTAL DRIVE FOR THE HIGH VOLTAGE CIRCUIT:
•
The Horizontal Blanking signal H Blk from Q706 is also sent to the High Voltage Driver IC IH01 pin ( 3 ).
This IC uses this signal as a Tickle Pulse signal to lock the high voltage H. Drive signal from IH01 pin 1 .
The high voltage H. Drive signal is output pin
1
and routed to the driver transistors,
QH02
. Then to the High
Voltage Horizontal Output Transistor QH01 . This transistor switches the primary of the Flyback transformer
TH01 . Deflection SW +115 is sent through pin ( 9 ) and output pin ( 10 ) to the collector of the Horizontal Out-
put Transistor
QH01
.
A sample of the High Voltage is output from the Flyback transformer
TH01 pin ( 12 ). This voltage is sent to pin
( 9 ) of the High Voltage Driver IC IH01 . This voltage is compared to the reference voltage available at pin ( 12 ).
(Continued on page 2)